1. Field of the Invention
The present invention relates generally to an ink passage having a first surface and a second surface which are adjacent to each other in an ink flow direction. In particular, the present invention is directed toward a platen for an inkjet recording device and an inkjet recording device in which ink droplets selectively ejected from a recording head smoothly are guided from the first surface to the second surface.
2. Description of Related Art
A known inkjet image recording device records an image on a recording sheet, e.g., a recording medium, by ejecting ink onto the recording sheet. The known inkjet recording device includes an inkjet recording head, and selectively ejects ink droplets from nozzles of the recording head. The ink droplet reaches the recording sheet, and a desired image is recorded on the recording sheet. In the known inkjet recording device, a plurality of recording sheets are stored in a feed cassette or a feed tray, and when printing is to be performed, a recording sheet is fed to a position directly below the recording head. A platen for an inkjet recording device is positioned directly below the recording head to support the recording sheet, such that the recording sheet faces the recording head.
As the accuracy of printing increases, a size of an ink droplet to be ejected from the recording head decreases, which may cause a small ink droplet that has not reached the recording sheet to float above the recording sheet. This floating ink droplet may be known as an ink mist. The ink mist may adhere to peripheral members of the recording head, such as the platen. Some of ink droplets ejected from the recording head may not reach the recording sheet, but may reach the platen, which is especially noticeable when printing is performed without a margin provided at an edge of the recording sheet. When the ink droplets adhere to the platen, the adhered ink droplets may be transferred to a subsequently fed recording sheet, and thus, the subsequent recording sheet may be contaminated, or an image formed on the subsequent recording sheet may be deteriorated, or both.
In another known inkjet image recording device, such as the inkjet image recording device described in Japanese Unexamined Patent Application Publication No. 2007-175971, an ink passage, such as a groove, is formed in an upper surface and a sidewall of a platen, and ink adhering to the upper surface of the platen is guided to a back surface of the platen by the ink passage. Because ink is removed from the upper surface of the platen, the ink may be prevented from adhering to the subsequently fed recording sheet. The ink guided to the back surface of the platen is further guided to an ink absorber, and is absorbed thereby.
A known platen may have a flat-plate shape and may include a synthetic resin, such as polystyrene or ABS. The known platen may be formed using by injection molding. A synthetic resin molded product is made by molding synthetic resin in a mold. For example, in two-plate molding, a mold is divided into two fixed and movable molds, and these molds are clamped with a predetermined amount of pressure to form a cavity. Heated and melted synthetic resin is injected into the cavity to make a synthetic resin molded product, the molded product is cooled, then the two molds are opened, and the synthetic resin molded product is removed. A mating surface of the two molds is known as a parting surface. A step-like mark is left on the synthetic resin molded product at an edge of the parting surface due to a minute displacement of the two molds from each other. For example, when a flat-plate platen is made by injection molding using a two-plate mold, a step-like mark generally is left at a side wall of the flat-plate platen. If a step-like mark is generated across the above-described ink passage, the flow of ink is interrupted by the step-like mark, and the ink accumulates at the edge of the parting surface.
For example, as shown in FIG. 9A, when a step-like mark 102 is formed substantially at a center portion of a side wall 101 of a platen 100, such that an upper side wall 104 horizontally protrudes beyond a lower side wall 105, the contact angle with respect to the side wall 101 of the ink droplet 103, which moves downward along the upper side wall 104 by a gravitational force, changes at the step-like mark 102, and a surface tension acting on the ink droplet 103, which acts to move the ink droplet 103 back to the upper side, increases. As a result, the ink droplet 103 remains at the step-like mark 102. Thus, in order to move the ink droplet 103 beyond the step-like mark 102 toward the lower side wall 105, an amount of drive force applied to the ink droplet 103 may need to be increased.
Similarly, as shown in FIG. 9B, when a step-like mark 102 is formed substantially at the center portion of the side wall 101 of the platen 100, such that the lower side wall 105 horizontally protrudes beyond the upper side wall 104, the ink droplet 103, which moves downward along the wall surface of the upper side wall 104 by a gravitational force, is supported by and remains on a horizontal surface of the step-like mark 102. When the size of the ink droplet 103 increases, the ink droplet attempts to move to the lower side wall 105 from the horizontal surface. At this time, the contact angle of the ink droplet 103 with respect to the side wall 101 changes, and the surface tension acting on the ink droplet 103, which acts to move the ink droplet 103 back to the horizontal surface, increases. As a result, the ink droplet 103 remains at the step-like mark 102. Thus, in order to move the ink droplet 103 beyond the step-like mark 102 toward the lower side wall 105, an amount of drive force applied to the ink droplet 103 may need to be increased.
As described above, when the ink accumulates at the step-like mark 102 on the side wall 101 of the platen 100, the flow of the ink from a front surface to a back surface of the platen 100 may be interrupted, and consequently, a recording sheet may be contaminated, or an image formed on the recording media may be deteriorated, or both.